Battery packs containing one or more batteries are used in many applications. For example, electric or hybrid electric vehicles are typically powered by one or more battery packs. As a battery pack is used and the batteries therein age, the batteries may need to be balanced with respect to their states of charge. The state of charge (SOC) of a battery, as used herein, is generally defined as the percentage of the full capacity of a battery that is still available for further discharge. Thus, the SOC of a battery may be used to regulate charging and discharging of the battery. Thus, it may be beneficial to track or monitor the SOC of one or more batteries during operation. Current techniques for tracking battery state of charge may include a coulomb-counting method that generates a coulomb count of the charge going into and out of the battery. Due to the accumulation of error in current measurements and step time, however, the accuracy of the coulomb-counting method may decrease over time.
Further, technologies for monitoring battery SOC include using a fixed maximum capacity value and runtime counter of the capacity consumed by the battery to determine a percentage of charge calculation based on charge units. This count, however, is often inaccurate due to cumulative errors in runtime readings, battery condition, variance of actual maximums, partial charges, and/or batteries charged externally.
In view of the aforementioned issues, it is desirable to provide a system and method for calibrating battery SOC so as to eliminate cumulative errors. Thus, the present disclosure is directed to a system and method for calibrating a battery state of charge by tracking accumulated capacity and/or time after a SOC calibration of the battery and initiating a SOC calibration when the accumulated capacity or time is beyond a predetermined threshold.